System for inducing a subject to fall to sleep

ABSTRACT

An assistance system for visually handicapped persons with visual impairment in a part of their visual field includes body-worn sensors to inform them actively about objects or movements in the visually impaired sides.

This application is a continuation of prior U.S. patent application Ser.No. 12/282,186, filed Sep. 9, 2008, which is a National StageApplication of PCT/IB2007/050645, filed Feb. 28, 2007, and which claimsthe benefit of European Patent Application No. 06111097.9, filed Mar.14, 2006, the entire contents of each of which are incorporated hereinby reference thereto.

TECHNICAL FIELD

The invention relates to a system for inducing a subject to fall tosleep.

BACKGROUND TO THE INVENTION AND PRIOR ART

Getting to sleep may not always be as self-evident as one would wish.Among causes of not falling to sleep are being overtired, pain and/orstress. It is known to arrange bedrooms to provide optimal conditionsfor inducing a subject suffering pathologic insomnia to fall to sleep,such as a comfortable bed, minimum light and reduced sound parameters.In addition, medications are known which render patients sleepy.However, it is also known that taking repeatedly such medication is notnecessarily beneficial to one's health.

Further, from U.S. Pat. No. 5,167,610 a sleep inducing system is knownbased on a respiration cycle detected as a biological signal.

From the prior art also sleep and environment control systems are knownto guide control processes, e.g. U.S. 2005/0143617. The system disclosedin U.S. '617 includes a respiration sensor capable of gathering sleepdata from a person and environment data during sleep using light as anenvironment control interface.

However, it has been found that conventional systems may notsatisfactory induce sleep in the subject.

It is therefore an object of the present invention to provide animproved system for inducing a subject to fall to sleep.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a systemfor inducing a subject to fall to sleep, comprising a light patterngenerator for generating a time varying light pattern in view of thesubject; a breathing rate measuring unit for measuring a breathingfrequency of the subject; and a control unit connected to the breathingrate measuring unit and the light pattern generator, for controlling thelight pattern generator, such that the generated light pattern has apattern frequency substantially between the measured breathing frequencyand a pre-selected desired frequency.

The invention is partly based on the observation that persons normallyhave a relatively low breathing frequency during a first stage of theirsleep.

The invention is further also based on the insight that persons tend tosynchronize their breathing rhythm to a cycle of light patterns, whichthey observe.

By providing a light pattern generator a time varying light pattern canbe generated in view of the subject, so that the subjects attention isdirectly or indirectly drawn to the time varying light pattern. Thebreathing rate measuring unit is arranged to measure the actualbreathing frequency of the subject. Further, by controlling the lightpattern generator, such that the generated light pattern has a patternfrequency substantially between the measured breathing frequency and thepre-selected desired frequency, a light pattern is obtained that has alower frequency than the actual breathing frequency, thereby leading thesubject to the pre-selected desired frequency. By choosing thepre-selected desired frequency to a value that corresponds to abreathing frequency of the subject wherein he/she falls to sleep, thesubject is thus deduced to reduce the breathing frequency to a breathingfrequency approaching the frequency that is natural when he/she falls tosleep. In doing so, the breathing frequency is a parameter, which iscontrolled in a control loop. Thereby, the breathing frequency isbrought in a more optimal status for falling to sleep in a relativelynatural manner, hence inducing the subject to actually falling to sleep.

In a preferred embodiment, the system comprises elements for forming acontrol loop of the breathing frequency of the subject.

It is noted that the pre-selected desired frequency might be chosen tobe an optimal breathing frequency averaged over a multiple set ofpersons. The pre-selected desired frequency might also correspond to thebreathing frequency of persons falling to sleep having personcharacteristics in common with the subject which is induced to fall tosleep, e.g. persons of a similar age, sex, etc. Moreover, thepre-selected desired frequency might correspond to the breathingfrequency of the subject himself or herself when falling to sleep, thuspersonalizing the system to the subject in question. Thereto, in apreferred embodiment according to the invention the pre-selected desiredfrequency is one, which has been found to bring on a sleeping state inthe subject. In general, the pre-selected desired frequency is lowerthan an actual breathing frequency of a subject that is not sleeping.

After repeated application of the abovementioned steps of measuring theactual breathing frequency and controlling the light pattern generator,such that the generated light pattern has a pattern frequencysubstantially between the measured breathing frequency and thepre-selected desired frequency, the subject is deduced to reduce thebreathing frequency further, thereby approaching the pre-selecteddesired frequency further, and hence further improving falling to sleepconditions. Then, the measured breathing frequency, the pre-selecteddesired frequency and the pattern frequency substantially coincide.Optionally, the system for inducing a subject to fall to sleep, or atleast the light pattern generator is switched off.

In a preferred embodiment according to the invention, the system furthercomprises a differentiator for determining a difference frequencybetween the breathing frequency and the pre-selected desired frequency,wherein the system is further arranged to determine the patternfrequency using the difference frequency and the breathing frequency. Byusing a differentiator the difference frequency to be eliminated caneasily be determined. Further, by using the difference frequency and themeasured breathing frequency, a new pattern frequency can be determinedthat might be selected between the actual breathing frequency and thepre-selected frequency.

In a further preferred embodiment the system comprises a limiter towhich a signal representing the difference frequency is input todetermine the pattern frequency, so that the pattern frequency cansimply be obtained by adding the limited difference frequency and theactual measured breathing frequency, the sum being between the actualbreathing frequency and the pre-selected frequency by definition.

In a preferred embodiment according to the invention, the limiter isarranged to limit the difference frequency between a pre-selectedminimum limit value and a pre-selected maximum limit value. In this waya simple, robust algorithm is obtained for leading the breathingfrequency to the pre-selected frequency.

In an alternative embodiment according to the invention, the limiter isarranged to limit the difference frequency between an adaptable minimumlimit value and an adaptable maximum limit value, thereby offeringpossibilities to adapt the minimum and maximum limit values of thelimiter during the process of reducing the breathing frequency of thesubject. As an example, the minimum and maximum limit values could beadapted in response to the response of the subject to the proposedbreathing frequency. It is noted that it is not necessary to provide alimiter with adaptable limit values. Due to the limiting processing stepof the limiter, the breathing frequency of the subject is smoothlyadjusted to the pre-selected desired frequency. However, by increasingthe limit values, the light pattern frequency will deviate more from thebreathing frequency of the subject, so that it is harder for the subjectto synchronize with the pattern frequency. By decreasing the limitvalues, the light pattern frequency will deviate less from the breathingfrequency of the subject, thereby making it easier for the subject tosynchronize. On the other hand, it will take longer before the subjectwill reach the desired breathing frequency.

In a preferred embodiment according to the invention, the control unitis also connected to a sound generating system for generating a timevarying sound, such that a cycle of the time varying sound substantiallyequals the pattern frequency. In doing so, the subject might be furthertend to synchronize his/her breathing frequency with the patternfrequency, so that an optimal condition for falling to sleep is fasterreached and/or chances that the subject will tend to adapt his/herbreathing frequency to the desired frequency, improve.

In a preferred embodiment according to the invention, the time varyinglight pattern comprises a sequence with objects having different opticalproperties, such as different shapes, different colors, differentpositions, and/or different light intensities, so that light patternshaving different optical images can be observed by the subject in orderto close the above-mentioned control loop.

In a further preferred embodiment according to the invention, the systemis arranged such that the light pattern objects become brighter, larger,have a larger wavelength and/or move from left to right during an exhalestage of the subject and that the light pattern objects become dimmer,smaller, have a smaller wavelength and/or move from right to left duringan inhale stage of the subject. It has been observed that subjects tendto synchronize their breathing frequency with the pattern frequencyeasier when the light intensity, the size, the wavelength and/or theposition of an object in the light pattern is synchronized with theactual breathing cycle as indicated above.

According to a second aspect of the present invention, there is provideda method for inducing a subject to fall to sleep, comprising the stepsof measuring a breathing frequency of the subject; selecting a patternfrequency between the breathing frequency and a pre-selected desiredfrequency; generating in view of the subject a time varying lightpattern having the pattern frequency; and repeating the above-mentionedsteps at a plurality of time intervals.

According to a third aspect of the present invention, there is provideda computer program product for processing data to induce a subject tofall to sleep, which computer program product comprises instructions forcausing a processor to perform the steps of selecting a patternfrequency between a measured breathing frequency of a subject and apre-selected desired frequency, for generating in view of the subject atime varying light pattern having the pattern frequency; and repeatingthe above-mentioned steps at a plurality of time intervals.

According to a fourth aspect of the present invention, there is provideda computer system, comprising a computer station being arranged toinduce a subject to fall to sleep by performing the steps of selecting apattern frequency between a measured breathing frequency of a subjectand a pre-selected desired frequency, for generating in view of thesubject a time varying light pattern having the pattern frequency; andrepeating the above-mentioned steps at a plurality of time intervals.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more fully understood, embodimentsthereof will now be described by way of example only, with reference tothe figures in which:

FIG. 1 shows a sleep inducing system according to an embodiment of thepresent invention;

FIG. 2 shows a first light pattern sequence;

FIG. 3 shows a second light pattern sequence;

FIG. 4 shows a third light pattern sequence;

FIG. 5 shows a fourth light pattern sequence, and

FIG. 6 shows a breathing cycle of a subject.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The figures are merely schematic views of preferred embodimentsaccording to an embodiment of the invention. In the figures, the samereference numbers refer to equal or corresponding parts.

FIG. 1 shows a system 1 for inducing a subject to fall to sleepaccording to the invention. The system 1 comprises a breathing ratemeasuring unit 2 for measuring a breathing frequency 6 of the subject.The unit 2 might e.g. comprise one or more acoustic, flow and/or opticalsensors and is preferably attached to the subject or installed in thebed or other suitable location, such as a chair etc. of the subject.

Further, the system comprises a light pattern generator 3 for generatinga time varying light pattern in view of the subject. The generatorcomprises means for projecting an image 14 on a surface, such as ascreen, wall and/or a ceiling near the subject, so that the subject canobserve the light pattern that is generated.

The system is also provided with a control unit connected to both thebreathing rate measuring unit 2 and to the light pattern generator 3.The control unit comprises an adder 12 and is arranged to control thelight pattern generator 3, such that the generated light pattern has apattern frequency 13 between the measured breathing frequency 8 and apre-selected desired frequency 5.

Further, the system comprises a differentiator 11 for determining asignal representing a difference frequency 9 between the breathingfrequency 8 and the pre-selected desired frequency 5, wherein the systemis further arranged to determine the pattern frequency 13 using thedifference frequency and the breathing frequency. In this process, thepattern frequency is selected between the breathing frequency and thepre-selected desired frequency. To that end, the system furthercomprises elements, among others the breathing rate measuring unit 2,the differentiator 11 and the control unit, for forming a control loopof the breathing frequency of the subject.

The system further comprises a limiter 4 to which a signal 9representing the difference frequency is input to determine theabove-mentioned pattern frequency 13. The output signal of the limiter 4is input to a first input port of an adder 12. The breathing frequency 8is input to a second input port of the adder 12, so that the adder 12computes the sum of the limited difference signal 9 and the breathingfrequency to obtain the pattern frequency 13.

It is noted in this context that information carried on a signal ispresented as such or as the information itself. As an example, in thiscontext a pattern frequency is similar to a pattern frequency signal.

In the embodiment shown in FIG. 1, the measured breathing frequency isfed to a frequency analyzer 7, e.g. for applying a band-pass filter tothe measured data. The frequency analyzer is further arranged to outputa signal that is a measure for the measured breathing frequency.

In one embodiment the limiter 4 is arranged to limit the differencefrequency between a pre-selected minimum limit value and a pre-selectedmaximum limit value. In a further embodiment the limiter 4 is arrangedto limit the difference frequency between an adaptable minimum limitvalue and an adaptable maximum limit value. By adapting the limit valuesone can synchronize the actual breathing frequency smoothly to thepre-selected desired frequency.

The pre-selected desired frequency is one, which has been found to bringon a sleeping state in the subject.

In addition, the control unit is further connected to a sound generatingsystem for generating a time varying sound, such that a cycle of thetime varying sound substantially equals the pattern frequency.

The time varying light pattern comprises a sequence with objects havingdifferent shapes, colors, positions and/or light intensities. Examplesof such object sequences are shown in FIGS. 2-5.

FIG. 2 shows a first light pattern sequence wherein an object sequence15-19 comprises objects having different shapes, in particular a disc15-19 having different diameters. The left window shows the pattern at astart instant t0, the window adjacent the left window shows the patternat a first instant t1, and so on until a fourth instant t4 is reachedwherein the cycle of the varying light pattern closes. The pattern atthe fourth instant t4 therefore equals the start instant t0. The shapeof the objects 15-19 may also vary by changing the outer perimeter ofthe object, e.g. by changing a disc to a triangular, etc. In this way, avariety of different shaped objects can be projected.

Similarly, FIGS. 3-5 show a second, third and fourth light patternsequence respectively, wherein object sequences 20-24, 25-29 and 30-34comprise objects having different colors, positions and lightintensities, respectively.

FIG. 6 shows a breathing cycle 35 of a breathing parameter Y of asubject as a function of time X. A first arrow 36 indicates an exhalephase and a second arrow 37 indicates an inhale phase, respectively ofthe breathing cycle 35. According to an embodiment of the invention, thesystem 1 may be arranged such that the light pattern objects 30-34 inFIG. 5 become brighter during an exhale stage of the subject and thelight pattern objects 30-34 may become dimmer during an inhale stage ofthe object.

It is noted that the system could also be arranged such that the lightpattern objects become larger, have a larger wavelength and/or move fromleft to right during an exhale stage of the subject and that the lightpattern objects become smaller, have a smaller wavelength and/or movefrom right to left during an inhale stage of the subject. As an example,the wavelength of such an object might change from blue to red during anexhale stage and change from red to blue again during an inhale stage ofthe subject.

Further, as the person skilled in the art will understand, combinationsof object variations could be made, e.g. an object that both changesposition and light intensity. Also multiple objects could be projectedin the light pattern.

The invention is not restricted to the embodiments described herein. Itwill be understood that many variants are possible.

Instead of using a limiter also other elements could be used to processthe difference signal, e.g. a processing filter.

Further, as the person skilled in the art will understand, the frequencyanalyzer can also be used for performing further processing steps on themeasured breathing data, such as a time to frequency transformation,frequency measuring, and/or other filter techniques in order to extracta base frequency of the subject's breathing.

In addition, it is noted that signals in the system shown in FIG. 1 canbe analogous or can be converted to digital signals, especially if acomputer system is applied to process data. The computer system theretocomprises a computer station.

Whilst specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. The description is not intended to limit theinvention. Any reference signs in the claims shall not be construed aslimiting the scope.

The invention claimed is:
 1. A system for inducing a subject to fall tosleep comprising: a light pattern generator for generating a timevarying light pattern in view of the subject; a breathing rate measuringunit for measuring a breathing frequency of the subject; and acontroller connected to the breathing rate measuring unit and the lightpattern generator, wherein the controller is configured to control thelight pattern generator such that the generated light pattern has apattern frequency which is different from the measured breathingfrequency, the pattern frequency being substantially between themeasured breathing frequency and a constant pre-selected desiredfrequency, wherein the constant pre-selected desired frequency is chosenfor the subject to bring on a sleeping state in the subject and isdetermined based on one of an average of breathing frequencies of aplurality of subjects and a breathing frequency of a person differentfrom the subject and having characteristics in common with the subject.2. The system according to claim 1, further comprising a differentiatorfor determining a difference frequency between the breathing frequencyand the constant pre-selected desired frequency, wherein the system isfurther arranged to determine the pattern frequency using the differencefrequency and the breathing frequency.
 3. The system according to claim2, further comprising a limiter to which a signal representing thedifference frequency is input to determine the pattern frequency.
 4. Thesystem according to claim 3, wherein the limiter is arranged to limitthe difference frequency between a pre-selected minimum limit value anda pre-selected maximum limit value.
 5. The system according to claim 3,wherein the limiter is arranged to limit the difference frequencybetween an adaptable minimum limit value and an adaptable maximum limitvalue.
 6. The system according to claim 1, further comprising elementsfor forming a control loop of the breathing frequency of the subject. 7.The system of claim 1, wherein the controller is further configured tochange the pattern frequency until a difference between the measuredbreathing frequency and the constant pre-selected desired frequency isminimized.
 8. The system according to claim 1, wherein the controllerfurther is connected to a sound generating system for generating a timevarying sound, such that a cycle of the time varying sound substantiallyequals the pattern frequency.
 9. The system according to claim 1,wherein the time varying light pattern comprises a sequence of theobjects having different shapes.
 10. The system a according to claim 1,wherein the time varying light pattern comprises a sequence with objectshaving different colors.
 11. The system a according to claim 1, whereinthe time varying light pattern comprises a sequence with objects havingdifferent positions.
 12. The system a according to claim 1, wherein thetime varying light pattern comprises a sequence with objects havingdifferent light intensity.
 13. The system a according to claim 1,wherein the time varying light pattern comprises a sequence with objectsthat become brighter, larger, have a larger wavelength and/or move in afirst direction during an exhale stage of the subject and that the lightpattern objects become dimmer, smaller, have a smaller wavelength and/ormove in a second direction during an inhale stage of the subject,wherein the first direction is different from the second direction. 14.The system of claim 13, wherein the first direction is opposite thesecond direction.
 15. The system of claim 1, wherein the patternfrequency is lower than the measured breathing frequency.
 16. Anon-transitory computer readable medium embodying computer instructionsfor inducing a subject to fall to asleep, wherein the computerinstructions, when executed by a processor, configure the processor toperform the acts of: allow choosing of a constant pre-selected desiredfrequency for the subject that brings on a sleeping state in the subjectand is determined based on one of an average of breathing frequencies ofa plurality of subjects and a breathing frequency of a person differentfrom the subject and having characteristics in common with the subject;cause an input to receive the constant pre-selected desired frequency;selecting a pattern frequency substantially between a measured breathingfrequency of a subject and the constant pre-selected desired frequency,for generating in view of the subject a time varying light patternhaving the pattern frequency; and repeating the selecting act at aplurality of time intervals, wherein the pattern frequency is differentfrom the measured breathing frequency.
 17. A computer system comprisinga computer station being arranged to induce a subject to fall to sleepby performing the acts of: choosing a constant pre-selected desiredfrequency for the subject that brings on a sleeping state in the subjectand is determined based on one of an average of breathing frequencies ofa plurality of subjects and a breathing frequency of a person differentfrom the subject and having characteristics in common with the subject;providing the constant pre-selected desired frequency; selecting apattern frequency substantially between a measured breathing frequencyof a subject and the constant pre-selected desired frequency, forgenerating in view of the subject a time varying light pattern havingthe pattern frequency; and repeating the selecting act at a plurality oftime intervals, wherein the pattern frequency is different from themeasured breathing frequency.
 18. A method for inducing a subject tofall to sleep, comprising the acts of: measuring a breathing frequencyof the subject; selecting a pattern frequency substantially between thebreathing frequency; choosing a constant pre-selected desired frequencyfor the subject that brings on a sleeping state in the subject and isdetermined based on one of an average of breathing frequencies of aplurality of subjects and a breathing frequency of a person differentfrom the subject and having characteristics in common with the subject;providing the constant pre-selected desired frequency; generating by alight pattern generator in view of the subject a time varying lightpattern having the pattern frequency; and repeating the measuring,selecting and generating acts at a plurality of time intervals until thebreathing frequency reaches the constant pre-selected desired frequencyindicating that the subject falls asleep, wherein the pattern frequencyis different from the measured breathing frequency.
 19. The method ofclaim 18, wherein the pattern frequency is lower than the measuredbreathing frequency.